1. Field of the Invention
The present invention relates to the use of adjuvants in topical ophthalmic compositions. In particular, this invention relates to the use of carrageenans and furcellarans in the compositions and a method for the controlled administration of a pharmaceutically active agent to patients wherein the topical compositions are administered as partially gelled liquids which thicken to form gels upon instillation into the eye. The transition from liquid to gel is primarily due to the change in ionic strength, especially an increase in the sodium chloride concentration.
2. Description of Related Art
Topical ophthalmic compositions have taken the form of liquids, ointments, gels and inserts. Liquid compositions for drop-wise instillation of pharmaceutically acceptable agents to the eye provide for easy formulation, but they do not always provide for an accurate dosage amount, as portions of the liquid are often blinked away during administration or drained down the punctum into the nasal passage. Ointments and gels, which usually reside in the eye longer than a liquid and therefore provide for more accurate administration, often interfere with a patient's vision. Ocular inserts, both bioerodible and nonbioerodible, are also available and allow for less frequent administration of drug; however, these inserts require complex and detailed preparation and are frequently uncomfortable to the wearer. An additional problem with the non-bioerodible inserts is that they must be removed after use.
U.S. Pat. Nos. 4,136,173 (Pramoda, et al.); 4,136,177 (Lin, et al.) and 4,136,178 (Lin, et al.) disclose the use of therapeutic compositions containing xanthan gum and locust bean gum which are delivered in liquid form and which gel upon instillation. In these three patents, the mechanism for transition from liquid to gel is due to a change in pH.
U.S. Pat. No. 4,861,760 (Mazuel, et al.) discloses ophthalmological compositions containing gellan gum which are administered to the eye as non-gelled liquids and which gel upon instillation due to the change in ionic strength.